This application is based on application No. 10-217124 filed in Japan, the contents of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image input device for generating a digital image signal by scanning a document, and relates more specifically to an image input device for detecting dust or other foreign matter on the optical input system for optically scanning a document.
2. Description of the Prior Art
Image input devices, such as image scanners and the scanning unit of a photocopying machine, whereby a CPU reads captured shading data and determines whether picture elements detected by a CCD sensor are normal picture elements or abnormal picture elements are known from the literature. See, for example, Japanese Patent Laid-Open Publication No. 6-6589.
Conventional image scanners for reading shading data and detecting normal and abnormal picture elements can also detect dust or other foreign matter on the shading panel. They are, however, unable to detect such dust or other foreign matter on the CCD sensor, the lens, and other parts of the optical input system. They are also unable to determine where the dust or other foreign matter is located.
It is therefore an object of the present invention to provide an image input device capable of determining a cleaning position when dust or other foreign matter is in the optical input system.
In addition to the above, it is a further object of the present invention to provide an image input device for informing the user of the position needing cleaning, that is, the cleaning position, when dust or other foreign matter is in the optical input system.
To achieve the above objects, an image input device according to the present invention comprises a scanning means for scanning a document image; an image noise position detector for capturing image data output from the scanning means, and detecting the main scanning address of noise information corresponding to image noise present in the image data; a focus calculating means for calculating focus information around the main scanning address detected by the image noise position detector; focus information storage for storing the focus information for each subscanning line; and foreign matter position determining means for determining the location of foreign matter on the scanning means based on the focus information stored in the focus information storage.
An image input device thus comprised according to the present invention first detects the main scanning address of any noise information corresponding to image noise in the image data, and then calculates focus information for the image elements in the area of the noise information. This focus information is stored for each subscanning line and used to determine the location of any dust or other foreign matter in the scanning means. It is therefore possible to know that there is dust in the input optics and where this dust is located. This makes it possible to reliably remove a cause of image noise in the output image, and thereby obtain a clear output image.
The scanning means preferably has a document platen glass on which an original document is placed; a light source for emitting light to scan an original document placed on the document glass while moving relative to the original document; a mirror for guiding reflected light from the original document to a lens system; a lens system for imaging light reflected thereto by the mirror on a photoelectric conversion element; and a photoelectric conversion element for outputting image data.
In this case, the foreign matter position determining means determines that foreign matter is present on the photoelectric conversion element or document platen glass if the focus calculating means determines that image focus is good; that foreign matter is on the photoelectric conversion element if focus is good and the foreign matter data width is large; that foreign matter is on the mirror or lens if focus is not good; and that foreign matter is on the mirror if focus is not good and there is a change in the focus information in the subscanning direction.
It will thus be obvious that an image input device according to the present invention can determine where dust or other foreign matter is present in the optical input system, that is, on the document platen glass, mirror, lens system, or photoelectric conversion element, based on the calculated focus information. It is therefore possible to detect where on what element of the optical input system dust or other foreign matter is present, and it is therefore possible to easily remove the dust or other foreign matter. The location of dust or other foreign matter in the optical input system can therefore also be displayed on an operating panel, for example, so that a user can easily know where the dust or other foreign matter is located on what part of the optical input system. Cleaning is thus made easier.
An image input device according to the present invention thus further preferably comprises a cleaning position indicating means for informing a user of the result detected by the foreign matter position determining means.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.